Hydrocarbons may be recovered from hydrocarbon containing formations by penetrating the formation with one or more wells. Hydrocarbons may flow to the surface through the wells. Conditions (e.g., permeability, hydrocarbon concentration, porosity, temperature, pressure) of the hydrocarbon containing formation may affect the economic viability of hydrocarbon production from the hydrocarbon containing formation. A hydrocarbon containing formation may have natural energy (e.g., gas, water) to aid in mobilizing hydrocarbons to the surface of the hydrocarbon containing formation. Natural energy may be in the form of water. Water may exert pressure to mobilize hydrocarbons to one or more production wells. Gas may be present in the hydrocarbon containing formation at sufficient pressures to mobilize hydrocarbons to one or more production wells. The natural energy source may become depleted over time. Supplemental recovery processes may be used to continue recovery of hydrocarbons from the hydrocarbon containing formation. Examples of supplemental processes include waterflooding, polymer flooding, alkali flooding, thermal processes, solution flooding or combinations thereof.
In chemical Enhanced Oil Recovery (EOR) the mobilization of residual oil saturation is achieved through surfactants which generate a sufficiently (ultra) low crude oil/water interfacial tension (IFT) to give a capillary number large enough to overcome capillary forces and allow the oil to flow (I. Chatzis and N. R. Morrows, “Correlation of capillary number relationship for sandstone”. SPE Journal, Vol 29, pp 555-562, 1989.) However, reservoirs have different characteristics (crude oil type, temperature and the water composition—salinity, hardness) and it is desirable that the structures of added surfactant(s) be matched to these conditions to achieve a low IFT. In addition, a promising surfactant must fulfill other important criteria including low rock retention, compatibility with polymer, thermal and hydrolytic stability and acceptable cost.
Compositions and methods for enhanced hydrocarbons recovery are described in U.S. Pat. No. 3,943,160 to Farmer et al., entitled “Heat-Stable Calcium-Compatible Waterflood Surfactant;” U.S. Pat. No. 3,946,812 to Gale et al., entitled “Use Of Materials As Waterflood Additives;” U.S. Pat. No. 4,077,471 to Shupe et al., entitled “Surfactant Oil Recovery Process Usable In High Temperature, High Salinity Formations;” U.S. Pat. No. 4,216,079 to Newcombe, entitled “Emulsion Breaking With Surfactant Recovery;” U.S. Pat. No. 5,318,709 to Wuest et al., entitled “Process for the Production of Surfactant Mixtures Based On Ether Sulfonated And Their Use;” U.S. Pat. No. 5,723,423 to Van Slyke, entitled “Solvent Soaps and Methods Employing Same;” U.S. Pat. No. 6,022,834 to Hsu et al., entitled “Alkaline Surfactant Polymer Flooding Composition and Process;” U.S. Pat. No. 6,269,881 to Chou et al., entitled “Oil Recovery Method For Waxy Crude Oil Using Alkylaryl Sulfonate Surfactants Derived From Alpha-Olefins and the Alpha-Olefin Compositions” and by Wellington, et al. in “Low Surfactant Concentration Enhanced Waterflooding,” Society of Petroleum Engineers, 1995; all of which are incorporated by reference herein.
U.S. Pat. No. 7,055,602 describes enhanced hydrocarbons recovery compositions containing aliphatic nonionic additives and/or the aliphatic anionic surfactants that have branched structures. These additives and surfactants may be primary alcohols or sulfates thereof having branched aliphatic groups which may have an average carbon number from 10 to 24, less than about 0.5 percent quaternary carbon atoms, an average number of branches per aliphatic group of the aliphatic anionic surfactant may range between about 0.7 and about 2.5, and methyl branches may represent between about 20 percent to about 99 percent of the total number of branches present in the group. Such compositions are shown in Table of that patent to achieve interfacial tensions of from 0.0022 (low range) to 1.9040 (high range) dynes/cm when used alone or in combination with other materials.